Not so much with a denial stage as it is a reluctance to accept the facts. I think there is a subtle difference, but no less destructive. I have emphysema as well as the primary culprit to my situation, but still try to push the limits that were now imposed upon me.
When I was first diagnosed, I was skeptical, but knew something was not right. I thought that perhaps I could re-condition myself to function 'properly' as I had done in the past with other issues I have suffered from. I am ex-military, and where are taught to adapt and overcome adversity.
I went through nearly a year of therapy. It did help to increase my initial losses in stamina, but plateaued far sooner than I had expected and with less than the desired results.
Learning to live with something that is trying to kill you is difficult, but denial is not constructive in any way. Acceptance and seeking ways to help corner and contain this disease has proven far more effective than trying to convince myself that it is something that I can rub a little dirt on and walk off.
Embrace those things that can contribute to stalling its advance rather than ignoring the facts that are in front of you. I know of very few folks out there who enjoy seeing their doctors. But they have a purpose. We need to use their expertise to help ourselves. Best wishes.